142 MANUAL OF THE MOLLUSCA. 



They are mostly confined to the fresh waters of warm regions. One sp. (N 

 fluviatilis) is found in Brit, rivers, and in the brackish water of the Baltic 

 Another extends its range into the brackish waters of the N. American rivers 

 And the West Indian N. viridis and meleagris, are fonnd in the sea. 



N. crepidularia has a continuous peristome, and approaches navicella ii 

 form ; it is found in the brackish waters of India. N. corona (Madagascar 

 is ornamented with a series of long tubular spines. 



Distr., 76 sp. W. Indies, Norway, Brit., Black Sea, Caspian, India 

 Philippines, Pacific, "W. America. 



Fossil, 20 sp. Eocene . Brit., France. &c. 



NAVICELLA, Lam. 



Etym.) navicella, a small boat. Type, N. porcellana. PI. IX., fig. 41. 



Shell obloug, smooth, limpet-like ; with a posterior, sub-marginal apex 

 aperture as large as the shell, with a small columellar shelf, and elongate 

 lateral muscular scars ; operculum very small, shelly. 



Distr., 18 sp. India, Mauritius, Moluccas, Australia, Pacific. 



FAMILY IX., TURBINID^. 



Shell spiral, turbinated or pyramidal, nacreous inside; operculum calca 

 rious and pauci -spiral, or horny and multi-spiral. 



Animal with a short muzzle ; eyes pedunculated at the outer bases of thi 

 long and slender tentacles ; head and sides ornamented with fringed lobes am 

 tentacular filaments (cirri) ; branchial plume single ; lingual ribbon long an( 

 linear, chiefly contained in the visceral cavity ; median teeth broad ; lateral 

 5, denticulated; uncini very numerous (sometimes nearly 100), slender, witl 

 hooked points (Fig. 15, A.). 



Marine, feeding on sea-weeds (algce). 



The shells of nearly all the turbinidse are brilliantly pearly, when tli 

 epidermis and outer layer of shell are removed ; many of them are used in th 

 state for ornamental purposes. 



TURBO, L. Top-shell. 



Etym., turbo, a whipping-top. 



Syn., batillus, marmorostoma, callopoma, &c. (Gray). 



Type, T. marmoratus. PI. X., fig. 2. 



Shell turbinated, solid ; whirls convex, often grooved or tuberculatec 

 aperture large, rounded, slightly produced in front ; operculum shelly ar 

 solid, callous outside, and smooth, or variously grooved and mammillate 

 internally horny and pauei-spiral. In. T. sarmaticus the exterior of the ope: 

 culum is botryoidal, like some of the tufaceous deposits of petrifying -( 



Animal with pectinated head-lobes. 



; wells. 



